Search Publications
The gravitational wave experiment
Comoretto, G.; Giampieri, G.; Asmar, S. W. +6 more
Since the optimum size of a gravitational wave detector is the wave length, interplanetary dimensions are needed for the mHz band of interest. Doppler tracking of Ulysses will provide the most sensitive attempt to date at the detection of gravitational waves in the low frequency band. The driving noise source is the fluctuations in the refractive …
EXOSAT Observations of the Be/X-Ray Binary 4U 2206+54
Saraswat, Priyamvada; Apparao, Krishna M. V.
We present the X-ray observations of the Be star binary system 4U 2206 + 54 made with the EXOSAT satellite during the period 1983-1985. The observations were carried out on three occasions, each separated by roughly a year. The source was active during the 1983 and 1985 observations and several short duration flares were observed. The spectrum, du…
Spatially Resolved Ultraviolet Spectroscopy of the Liner Galaxy NGC 3998
Filippenko, A. V.; Branduardi-Raymont, G.; Reichert, G. A. +3 more
We report results of recent IUE observations of the low-ionization nuclear emission-line region (LINER) galaxy NGC 3998. Spatial structure in the long-wavelength emission is apparent; the spatial profiles in the LWP images show a two-component structure, with an unresolved central component superposed on extended underlying emission. We have used …
Carbon and Nitrogen Abundances Determined from Transition Layer Lines
Mena-Werth, Jose; Boehm-Vitense, Erika
The possibility of determining relative carbon, nitrogen, and silicon abundances from the emission-line fluxes in the lower transition layers between stellar chromospheres and coronae is explored. Observations for main-sequence and luminosity class IV stars with presumably solar element abundances show that for the lower transition layers Em = BT<…
Rotation and Transition Layer Emission in Cool Giants
Boehm-Vitense, Erika
Gray (1981, 1982) found that field giants with T(eff) less than about 5500 K experience a steep decrease in rotational velocities coupled with a decrease in transition layer emission. This decrease may be attributable to fast magnetic braking or to redistribution of angular momentum for rapidly increasing depths of the convection zones if these ro…
A study of the optical and ultraviolet spectral characteristics and the circumstellar material around the new luminous blue variable WRA 751.
Perez, M. R.; The, P. S.; de Winter, D. +1 more
The LBV characteristics of the new LBV candidate WRA 751 suggested by Hu et al. (1990) are studied in greater detail. A comparison is made with observational characteristics of the well-known LBVs Ag Car and HR Car using photometric and spectroscopic data of Hu et al. supplemented with an IUE spectrum and direct CCD images in H-alpha, blue, and re…
The Characteristics and Origin of the Gould's Belt
Torra, J.; Comeron, F.; Gomez, A. E.
Some statistical studies on the nearby early-type stars proposed for observations by HIPPARCOS are presented. Results on spatial orientation and kinematics are in agreement with those found in the literature. An age estimate based on non-kinematical hypothesis is found to be somewhat smaller than expansion ages derives by some authors. Finally, it…
A new kind of oscillation in the persistent emission of the Rapid Burster.
Stella, Luigi; Lewin, Walter H. G.; van Paradijs, Jan +3 more
We present a study of a new kind of oscillation found in the persistent emission after some type II bursts from the Rapid Burster observed during 1985 August with EXOSAT. All 95 bursts observed were longer than 30 s. Ten of them were followed by these oscillations. The frequency of the oscillations ranged from 39 to 56 mHz. A period decrease (by 3…
The active phase of the symbiotic star BF Cygni.
Gonzalez-Riestra, R.; Cassatella, A.; Fernandez-Castro, T. +1 more
The activity phase of BF Cygni discovered in May 1989 and which lasted about two years is examined. The UV emission lines, usually strong during quiescence, were not detectable during the outburst. UV high-resolution spectra in the outburst indicate the development of an expanding shell giving rise to a considerable number of violet-shifted absorp…
The Binary Cepheid BP Cir: A Test of Evolutionary Tracks
Arellano Ferro, A.; Evans, Nancy R.; Udalska, Joanna
IUE spectra of the system containing the Cepheid BP Cir are used to derive the magnitude difference between the two stars (Δ V = 1.88 ± 0.3 mag) and the spectral type of the companion (B6.OV). This is the first system yet encountered for which the standard Seaton reddening law is inappropriate. For BP Cir, a stronger 2200 Å bump than the standard …